JPH01185656A - Developer - Google Patents

Abstract

PURPOSE:To prevent exposing of magnetic powder on a carrier surface and to obtain a developer which has a high electrostatic charge quantity and does not splash by specifying the sphericity grain size and fluctuation coefft. of a toner of a two-component developer consisting of a toner and binder type carrier. CONSTITUTION:The sphericity of the toner of the two-component developer consisting of the toner and the binder type carrier is specified to <=150, the average grain size to <=14mum and the fluctuation coefft. to <=15%. The grain size is reduced to <=14mum in order to obtain a high-grade image and the toner is formed to the spherical shape having <=150 sphericity and <=15% fluctuation coefft. in order to prevent the degradation in flowability. On the other hand, the binder type carrier to be used for the spherical toner of the small grain size is treated with an acid to elute away the magnetic powder exposed on the surface so that the environmental resistance is stabilized. The developer with which the sufficient electrostatic charge quantity is obtainable and which has the stable electrostatic charge quantity even at and under a high temp. and high humidity and obviates toner splashing is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developer, and particularly to a developer capable of copying and developing small-particle toner particles with high precision and high image quality without scattering.

BACKGROUND ART AND PROBLEMS As electrophotographic copying devices have become more widely used, there has been a growing demand for high-definition, high-quality images with excellent line reproducibility, halftone dot reproducibility, half-dot reproducibility, etc. became. In order to satisfy such requirements, it is desirable to make toner particles as small as possible and have a sharp particle size distribution. Sharpening the particle size distribution improves line reproducibility, halftone reproducibility, half reproducibility, etc., and also sharpens the charge amount distribution.
It also greatly contributes to improving image quality such as texture. Techniques for regulating particle size distribution include, for example, Japanese Patent Publication No. 57-24369, Japanese Patent Application Laid-Open No. 106554-1982, and Japanese Patent Application Laid-open No. 61-27.
No. 5766, Japanese Patent Application Laid-open No. 61-275767, etc. are known.

However, reducing the particle size of the toner simultaneously reduces the fluidity of the toner itself and as a developer. Therefore, in order to prevent the fluidity of the toner or developer from decreasing, it is desirable to further spheroidize the toner.

When toner is spherical, another problem arises in that the probability of contact with a carrier is low due to the spherical shape of the toner, resulting in a low charging ability. In other words, even if a ferrite carrier, which is commonly used for small particle size spherical toner with a small particle size distribution, is used, the absolute amount of charge required for the toner is insufficient, and the charge amount distribution is This causes problems such as a large amount of toner scattering, and the resulting image has a lot of fog.

In addition, if a binder type carrier, which is commonly used for small particle size spherical toner with a small particle size distribution, is used, although a certain degree of chargeability can be obtained, the amount of charge depends on the environment due to the influence of the magnetic powder exposed on the surface. Under high temperature and high humidity conditions, the amount of charge decreases, leading to problems such as a significant increase in dust scattering.

Problems to be Solved by the Invention As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have developed a toner with a small particle size distribution and a spherical shape, and a binder-type carrier with no exposed magnetic powder on the surface. It was discovered that when used in combination with the above, a sufficient amount of charge can be obtained, the amount of charge is stable even under high temperature and high humidity, and a developer with excellent toner scattering prevention can be obtained, and the present invention was completed. It arrived.

That is, the present invention uses a small particle size, spherical toner with a small particle size distribution as a toner, and a sufficient amount of charge can be obtained, the amount of charge is stable even under high temperature and high humidity, and there is little toner scattering. The purpose is to provide a developer.

Means for Solving the Problems That is, the present invention provides a two-component developer containing a toner and a binder type carrier, in which the toner has a sphericity of 150 or less, an average particle diameter of 14 μm or less, and a coefficient of variation of 15% or less. , relates to a developer characterized in that a binder type carrier has no exposed magnetic powder on its surface.

From the viewpoint of obtaining a high-quality image, it is preferable that the toner particle size is smaller, the sphericity is higher, and the average particle size distribution is smaller.

However, the smaller the particle size of toner, the less the fluidity, toner scattering properties, and toner chargeability. In fact, even if small particle size toner is used, fogging etc. occur and high quality images cannot be obtained.

Fluidity is generally one of the major properties required of toners, but it is particularly an important problem for toners with small particle diameters, which are one of the conditions for achieving high-quality images as shown in the present invention. Generally, the fluidity is better as the toner particle size is larger, the particle size distribution is sharper, and the shape is closer to a spherical shape. Average grain size is 14μ in terms of image quality etc.
It is necessary to reduce the particle size to less than 10 μm, preferably 2 to 10 μm, and to make the toner spheroidal in order to improve fluidity. From this point of view, the toner has characteristics such that the sphericity (SF) value of the toner is 150 or less, preferably 140 or less, and the coefficient of variation, which is a measure of the particle size distribution of the toner, is 15% or less, preferably 10% or less. It is preferable to have the following.

The sphericity is expressed by the following formula [1]: [In the formula, the maximum flame represents the average value of the maximum flame in the projected image of the toner particles, and the area represents the average value of the projected area of the toner particles].

The sphericity SF is used as a parameter indicating the difference between the major axis/minor axis (distortion property) of the toner, and generally indicates the sphericity of the powder particles, and the closer the particle shape is to a sphere, the closer to 100 the value becomes.

In the present invention, sphericity SF refers to a value measured by an image analyzer (Luzex 5000; manufactured by Nippon Regulator Co., Ltd.), but in general, when measuring sphericity SF, there is not a large difference depending on the model, so This does not mean that the measurement must be performed with the above-mentioned model in particular.

The coefficient of variation is determined by taking a photo with a scanning electron microscope, measuring the particle size of 100 particles at random, and calculating the standard deviation (σ) from the average particle size ('X). The value (%) obtained by dividing by and multiplying by 100 represents the measure of dispersion (%).

The standard deviation is calculated as the square root of the square of the difference from the average value of each measured value divided by (n-1) when n particle diameters are measured. That is, it is expressed by the following equation.

[In the formula, X3, x2..., Xn are measured values of particle diameters of sample particles, and X is the average value of n measured values. ] In the present invention, the toner average particle size is a value obtained by measuring the relative weight distribution by particle size with a 100 μm aperture tube using Coulter Counter (manufactured by Coulter Counter).

The small particle size spherical toner having a small particle size distribution used in the present invention as described above has a smaller contact probability, contact area, etc. with the carrier. From this point of view, in the case of a developer that is randomly combined with carriers that do not take into account the chargeability of the toner as described above, the amount of charge required for the toner characteristics cannot be obtained sufficiently, and the toner Splashing becomes a problem.

In addition, in the case of a developer in which the carrier is selected by focusing only on the charging characteristics of the toner and without taking environmental stability into account,
The environmental dependence of the carrier greatly affects the environmental stability of the developer, resulting in problems such as a decrease in the amount of charge and a significant increase in toner scattering under high temperature and high humidity conditions.

In the present invention, it has been found that the above problem can be solved by combining a toner with a binder-type carrier in which magnetic powder is mixed in a binder resin, and the magnetic powder is not exposed on the surface of the carrier.

As the resin used in the binder type carrier of the present invention, a generally known thermoplastic resin is used. In particular, acrylic resins having polar groups such as carboxyl groups, hydroxyl groups, glycidyl groups, and amino groups are mentioned, for example,
Acrylic acid monomers such as methacrylic acid, acrylic acid, maleic acid, and itaconic acid; Heptamers having hydroxyl groups such as hydroxypolypropylene monomethacrylate and polyethylene glycol monomethacrylate; Monomers having amino groups such as dimethylaminoethyl methacrylate:
Examples include those obtained by copolymerizing glycidyl methacrylate or the like with lower alkyl acrylate and/or styrene. Also, polyester resins such as ethylene glycol, triethylene glycol, 1.2-7'
Examples include polyester resins obtained by condensation polymerization of polyols such as propylene glycol and l,4-butanediol and dicarboxylic acids such as maleic acid, itaconic acid, and malonic acid, and thermoplastic resins such as epoxy resins. These resins may be three-dimensionally crosslinked to adjust their viscosity.

On the other hand, the magnetic material blended into the binder-type carrier is not particularly limited, but in the case of obtaining the carrier used in the present invention by eluting and removing magnetic powder on the carrier surface by acid treatment, hydrochloric acid, sulfuric acid, nitric acid, Any material may be used as long as it is soluble in acids such as acetic acid, such as metals such as iron, nickel, and cobalt, and these metals and zinc, antimony, aluminum, lead, tin, bismuth, beryllium, manganese, selenium, tungsten, and zirconium. , alloys with metals such as vanadium or mixtures thereof, mixtures with metal oxides such as iron oxide, titanium oxide, magnesium oxide, ferromagnetic ferrite, magnetite, and mixtures thereof.

The particle size of these magnetic materials is 2 μm or less, preferably 1 μm or less as a primary particle. If the particle size of the magnetic powder is larger than 2 μm, uniform dispersion in the binder becomes difficult due to the relationship with the particle size of the preferred binder-type carrier, making it impossible to obtain a homogeneous carrier, and the carrier particles become brittle.

The mixing ratio of the resin and the magnetic powder is 100 to 900 parts by weight, preferably 200 parts by weight of the magnetic powder per 100 parts by weight of the resin.
~800 parts by weight. If the amount of magnetic powder mixed is more than 900 parts by weight, the magnetic powder becomes secondary particles and is not uniformly dispersed, making the carrier particles brittle, and kneading performance, that is, productivity, also decreases. On the other hand, if it is less than 100 parts by weight, sufficient magnetism cannot be obtained.

The carrier of the present invention may further contain a dispersant.

Examples of the dispersant include carbon black, colloidal silica, colloidal titanium, colloidal alumina, etc., and these are preferably blended in the carrier in an amount of 1 to 3% by weight at 0°O.

The binder type carrier of the present invention may further contain a charge control agent, and may also contain other commonly known additives.

To manufacture a binder type carrier using the above components, for example, after thoroughly mixing the materials with a mixer etc.,
It is pulverized, then melted and kneaded using an extrusion kneader. After cooling the obtained kneaded material, it is finely pulverized and classified to obtain a binder type carrier.

The appropriate size of the carrier is 20 to 70 μm, preferably 30 to 60 μm, in view of the size of the toner particles required in the present invention. If it is larger than 70 μm, the specific surface area of the carrier becomes small and at the same time the mixing and agitating properties as a developer deteriorate, and not only the charging stability and the effect of preventing toner scattering, which are the objects of the present invention, cannot be obtained sufficiently, but also This also has a negative effect on image quality such as fine resolution and gradation. Also, during mixing and stirring,
This promotes the occurrence of fusion of toner and developer, which becomes a problem. If the diameter is smaller than 20 μm, the fluidity of the developer decreases, resulting in poor mixing and agitation performance, and the above effects cannot be fully achieved. Also, the magnetic force of the carrier becomes insufficient and the carrier tends to adhere to the photoreceptor.

From the binder type carrier obtained as above,
In order to eliminate the magnetic powder exposed on the surface, measures such as (1) eluting and removing the magnetic powder exposed on the surface with acid, and (2) coating the binder type carrier with a resin can be taken.

Acids used in the acid treatment method (■) include hydrochloric acid, sulfuric acid,
Examples include mineral acids such as nitric acid, and organic acids such as acetic acid.

The acid treatment may be performed so that the magnetic powder is not exposed on the carrier surface. To prevent magnetic powder from being exposed on the surface, preferably 0.5 μm from the carrier surface.
It is desirable to elute an amount equivalent to the magnetic powder present at a depth greater than or equal to the depth. More preferably, 1.0 μm from the carrier surface
It is desirable to elute an amount equivalent to the magnetic powder present at a depth greater than or equal to the depth. If it is less than 0.5 μm, there is a possibility that the magnetic powder will be exposed on the surface due to wear of the carrier during continuous printing.

The acid treatment conditions such as the concentration of the acid used and the immersion time are appropriately selected depending on the type of acid, the magnetic powder used, the temperature conditions, etc.

Methods for testing the amount of magnetic powder seeds include, but are not limited to, the following. Prepare in advance a calibration curve obtained by dissolving the magnetic powder contained in the binder-type carrier in the acid to be used. This can be done by using a spectrophotometer to measure the absorption spectrum of the acid, which changes as the magnetic powder melts.

Further, whether or not magnetic powder is exposed on the surface of the binder type carrier can also be verified using a surface analysis method such as Auger analysis.

To acid-treat a binder-type carrier, for example, acid is added to the carrier and sufficiently dispersed using a stirring device such as ultrasonic vibration. Next, after stirring using a starcooter, the supernatant is discarded by decantation, water is added, and ultrasonic cleaning is performed. Repeat this several times, collect the carrier by suction filtration, and finally dry it.

When the magnetic powder is removed from the surface of the binder-type carrier in this manner, many irregularities are formed on the surface of the carrier. This means that the surface area of the carrier increases significantly, so that the toner can obtain a sufficient amount of triboelectric charge.

In order to eliminate the exposure of the magnetic powder exposed from the surface of the binder-type carrier by method Either by spraying onto the binder-type carrier particles and drying them, or by mechanically mixing the carrier particles and polymer fine particles using a blender mill, Henschel mixer, etc., adhering the fine particles to the surface of the carrier, and then dissolving and fixing them by heating, melting, etc. There are ways to do this. Specific equipment for this purpose includes an autoclave with a stirrer, a sparr flow (manufactured by Freund Sangyo Co., Ltd.), a normal spray drying device, and an impact reformer combined with thermal treatment (for example, the Nara Hybridizer (manufactured by Nara Kikai Seisakusho Co., Ltd.)). , Ongmil (manufactured by Hosokawa Micron), and the like.

The amount of resin coated on the binder type carrier may be sufficient as long as it can cover the magnetic powder exposed on the surface, and preferably the thickness of the coating layer is 0.05 to 6 μm. If the thickness of the coat layer is less than 0.05 μm, the magnetic powder may be exposed on the surface due to wear of the carrier during printing, and if it is thicker than 6 μm, the coat layer is likely to peel off.

The toner used in the present invention may be a toner prepared by any known method as long as it is used in a two-component development method, such as a kneading and pulverization method, a suspension polymerization method, a microcapsule method, and a spray drying method. The small particle size spherical toner with the sharp particle size distribution required by the present invention can be obtained by appropriately selecting the manufacturing conditions in each of the above manufacturing methods. It can be prepared by spheroidizing by thermal and/or mechanical methods, etc., or by classification using methods such as air classification [However, if the coefficient of variation obtained by seed polymerization method etc. is 10% It is preferable to use a capsule toner obtained by laminating toner components such as a colorant, a resin, a charge control agent, and a wax on the particle surface as described below in terms of characteristics and production yield. If necessary, treatments such as heat treatment, wet or dry coating treatment, surface dissolution or swelling treatment with an organic solvent, etc. may be performed.

Of course, the toner may contain a charge control agent, the charge control agent may be adhered and fixed to the surface of the toner, and other known additives may also be added and contained.

The developer of the present invention has a carrier and a toner of toner 1 to 2Qw.
It is used by mixing at a ratio of t%.

The developer of the present invention further contains silica, titanium oxide, alumina, etc. to improve fluidity or cleaning properties.
A post-treatment agent such as metal soap may be added and mixed.

Monodisperse spherical copolymer of styrene and n-butyl methacrylate obtained by seed polymerization method (average particle size: 8 μm, glass transition temperature: 54°C: softening point: 128°C)
) and 8 parts by weight of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd.: MA#8) were placed in a 1012 Henschel mixer and mixed and stirred at a rotational speed of 1500 rpm for 2 minutes to adhere carbon black to the surface of the polymer particles. Next, carbon black was immobilized on the surface of the polymer particles by treatment for 3 minutes at 9000 rpm using a Nara Kikai Hybridization System NH3-1 model.

Furthermore, polymer particles 1 treated with the above carbon black
00 parts by weight and PMMA particles MP-145■ (manufactured by Soken Kagaku Co., Ltd.: average particle size 0.15 μm, glass transition temperature 125°C)
A PMMA resin coating layer was formed by treating 10 parts by weight in the same manner as above. Furthermore, the obtained t; polymer particles 1
By applying 0.5 parts by weight of a negative charge control agent chromium complex dye Spiron Black TRH (manufactured by Hodogaya Chemical Industry Co., Ltd.) to 00 parts by weight in the same manner as above, Spiron Black TRH was added to the surface of the toner. The average particle size is 8゜3.
A toner a with a sphericity of 132 μm and a coefficient of variation of 8% was obtained.

Further, toners b-c were obtained by the same manufacturing method as toner a, except that the materials used for toner manufacturing were changed to those shown in memorial service 1.

(Hereinafter, blank space) Toner production example d Ingredients - Styrene 70 parts by weight - n-butyl methacrylate 30 parts by weight - 2,2-azobis-(2,4-0,5 parts by weight dimethylvaleronitrile) - Carbon black MA# 8 8 parts by weight (manufactured by Mitsubishi Chemical Industries, Ltd.) Chromium complex dye Spiron 5 parts by weight Black TRH (manufactured by Hodogaya Chemical Industries, Ltd.) The above materials were thoroughly mixed using a sand stirrer to prepare a polymerizable composition.

This polymerizable composition was added to an aqueous gum arabic solution with a concentration of 3% by weight, and the polymerization reaction was carried out at a temperature of 60°C for 6 hours while stirring at a rotational speed of 4000 rpm using a stirrer rT-K Auto Homo Mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). and further increase the temperature to 8
The temperature was raised to 0°C to cause a polymerization reaction. After the polymerization reaction was completed, the reaction system was cooled, washed with water five times, filtered and dried, and then air classified to obtain spherical particles.

The average particle diameter of the obtained spherical particles was 14 psi (softening point (Tm)) and 61° C. (C1 glass transition point (Tg)).

By classifying the obtained particles, the average particle size was 8゜4μm.
, a toner d with a sphericity of 117 and a coefficient of variation of particle size distribution of 14%.
I got it.

Toner production example e In toner a, the charge control agent was nigrosine base EX (
By changing the amount to 0.6 parts by weight (manufactured by J. Endo Kagaku Kogyo Co., Ltd.), a toner having an average particle size of 8.2 μm, a sphericity of 131, and a coefficient of variation of 8% was obtained. The toner obtained here is designated as e.

・Polyester resin 100 (softening point 12)
3°C1 Glass transition point 65°C)・Inorganic magnetic powder
500 (manufactured by Toda Kogyo Co., Ltd., EPT-1000
) ・Carbon black 2 (manufactured by Mitsubishi Chemical Industries, Ltd., MA#8) The above materials were thoroughly mixed and pulverized using a Henschel mixer, and then the cylinder part was heated to 180°C5.
The mixture was melted and kneaded using an extrusion kneader set at 0°C. After allowing the mixture to cool, it was coarsely pulverized using a feather mill, further finely pulverized using a jet mill, and then classified using a classifier to obtain a magnetic carrier having an average particle size of 55 μm.

Let this carrier be carrier A.

Method for producing carrier B (hydrochloric acid immersion treatment of carrier A) Carrier A obtained in the production of carrier A was subjected to the following hydrochloric acid treatment.

Add 6N hydrochloric acid 5001IIQ to 1 kg of carrier.

Sufficiently disperse the carrier using ultrasonic vibration, etc. The mixture was then stirred for 1 hour using a three-kun motor. The supernatant was discarded by decantation, water was added, and ultrasonic cleaning was added. This was repeated eight times, and the carrier was collected by suction filtration. Then, vacuum drying (60°C, 2 hours) was performed.

The obtained carrier is called carrier B.

Manufacturing method of carrier C In the manufacturing method of carrier A, KBC-200 is used as magnetic powder.
(Average particle size 0.5 μm) (manufactured by Kanto Denka Kogyo Co., Ltd.) 50
A binder-type carrier was manufactured in the same manner as in the manufacturing method of Carrier A except that 0 parts by weight was used.

The obtained carrier is designated as carrier C.

Manufacturing method of carrier D In the manufacturing method of carrier B, MFP-2 (
The carrier was treated in the same manner as in Example 1, except that 6 N H2S O4 was used as the acid in the acid treatment of the carrier, and the stirring operation was performed at 60 °C for 1 hour and 30 minutes. It's a good deal;.

The obtained carrier is designated as carrier D.

Manufacturing method of Carrier E Bisphenol type polyester resin (softening point 123°C
;Glass transition point 65°C) was adjusted to 2% toluene solution, and 3000 parts by weight of Carrier A was sprayed at a spray pressure of 3.59/cm using Spiller Coater 5P-40 (manufactured by Kaida Seiko Co., Ltd.), and sprayed with 14097. The particles were treated for 120 minutes at a temperature of 50° C., and aggregates were removed using a sieve (sieve opening 105 μm) to obtain a coated carrier.

The obtained carrier is called carrier E.

Example 1 Part by weight of the aforementioned toner aiooo was post-treated with 0.1 part by weight of colloidal silica R-972 (manufactured by Nippon Aerosil Co., Ltd.). Toner 29 thus obtained and the carrier B289 described above were placed in a 50 cc polyethylene bottle, placed on a rotating stand, and rotated at 120 rpm for 24 hours.The toner charge amount was measured and showed a good value of -18 μC/9. Further, when the amount of scattering at that time was examined, it was found to be very small at 86 cpm, which is a value that poses no problem in practical use. After that, this developer was stored in an environment of 35°C and 85RH% for 24 hours, and the amount of charge and amount of scattering were measured.
It was stable at 17 μG/9.98 and had little environmental dependence.

The amount of scattering was measured using a digital dust meter model P5H2 (manufactured by Somede Kagaku Co., Ltd.). The dust meter and magnet roll are
After setting 2g of developer on this magnet roll, set the magnet at a distance of 2000r.
The dust meter reads the toner particles generated when rotating at pm as dust, and the number of counts per minute is cpm.
Display in .

Examples 2 to 7 The same evaluation as in Example 1 was performed using the toners and carriers shown in Table 2, and as a result, each showed good values. See Table 2 for results.

Comparative Example 1.2 The same evaluation as in Example 1 was carried out using the carrier as the toner shown in Table 2. As shown in Table 2, the attenuation of the charge amount was large and the amount of scattering increased significantly in all cases.

(Hereinafter, blank space) Effects of the invention Small particle size spherical toner with a sharp particle size distribution, with an average particle size of 14 μm or less, a sphericity SF of 150 or less, and a coefficient of variation of 15% or less, has magnetic powder exposed on the surface. The developer is composed of a binder-type carrier that does not have a binder-type carrier, and in this combination, even small spherical toner particles with a small particle size distribution can be quickly and uniformly mixed and stirred and uniformly charged, which is effective in suppressing toner scattering. It is possible to obtain high-quality images without fogging, taking advantage of the small particle size spherical toner, which is less dependent on the environment and has a narrow particle size distribution.

Patent applicant: Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. In a two-component developer containing a toner and a binder type carrier, the toner has a sphericity of 150 or less and 14μ
A developer characterized in that it has an average particle size of not more than m, a coefficient of variation of not more than 15%, and a binder type carrier with no exposed magnetic powder on its surface. 2. The developer according to claim 1, wherein the magnetic powder is eluted and removed with acid so that the magnetic powder is not exposed on the surface of the binder type carrier. 3. The developer according to claim 1, wherein the binder type carrier is coated with a resin so that the magnetic powder is not exposed on the surface of the binder type carrier.